Beijing: Chinese businessman Li Hua suffered a stroke, has considered suicide, and his wife has been hospitalised with heart trouble, all since their daughter went missing on flight MH370.

A. Amirtham, a retired Malaysian clinic worker, suffers fainting spells and a lack of sleep and appetite over the disappearance of her only son Puspanathan.

Li Jiuying is tormented by the loss of her big brother Li Guohai and the burden of lying to their elderly mother that he was not on the flight. The mother believes he is tied up with a business dispute.

One year after the Malaysia Airlines jet vanished, next of kin are trapped inside what one describes as a "black hole" of emotional and often physical suffering.

Li Hua, 58, who only recently recovered the full use of his left arm following last year's stroke, used to be a fitness buff.

"Now I just feel sick," he said, chain-smoking.

"I have thought of suicide but... why? I need to stay alive for my wife and fight for the truth."

But the truth remains painfully elusive for families as the tragedy's March 8 anniversary nears.

In one of aviation's most baffling mysteries, the Boeing 777 with 239 people aboard inexplicably detoured from its Kuala Lumpur-Beijing route, heading west and south into the Indian Ocean and history.

A year-long search in that ocean's remote southern reaches – now focussed on high-tech sonar scanning of the seabed – has found nothing.

The vanishing act is not without some concrete outcomes.

World aviation authorities last month mandated minute-by-minute tracking of aircraft in distress, beginning globally next year, to prevent a recurrence.

This week, Australia said it also was conducting trials, with Malaysia and Indonesia, of a system that increases the frequency with which planes are tracked over remote oceans.

But all of that is little comfort now for MH370 families.

They endured an emotional trial of false leads and dashed hopes during Malaysia's chaotic initial response, which included its air force's failure to act despite tracking the plane shortly after it diverted.

Many are now incensed over the January 29 declaration that all on board were presumed dead and families should seek compensation.

Next of kin fear the move means the Malaysian government and airline are poised to declare the matter closed without any resolution.

"There is no closure for us," said Grace Subathirai, a Malaysian attorney whose mother Anne Daisy was on board.

"It has totally changed our lives. Nothing can ever be the same."

Malaysian authorities have revealed no new information for months, and said in January the disappearance remains a mystery.

The government and airline insist they are being transparent and are committed to the Australia-led search. Both declined interview requests.

For many relatives, grief is compounded by the perceived callous attitude of the Malaysians and suspicions that the full truth is not being told.

Among the hardest hit are families from China, whose nationals comprised two-thirds of the passengers. Many lost their sole offspring under China's one-child policy.

Nearly two dozen Chinese relatives have been in Malaysia since last month to press authorities for answers. They say they have been rebuffed.

Many complain of sleeplessness, appetite loss, panic attacks and more serious ailments like hypertension and heart problems.

Several said they had not returned to their homes since last March 8.

"How can we go back? We would see his things. It is too painful," said Wang Rongxuan, 60, who lost her 37-year-old son Hou Bo.

Angrily rejecting the notion that he is dead, Wang burst into tears, insisting he would return.

MH370 families are suffering what is called "ambiguous loss", the disappearance of loved ones with no clue to what happened, said Sarah Wayland, a Sydney-based expert on counselling relatives of missing persons.

"People become frozen to the time that person went missing," she said.

"The only way for many to survive is to accept that they may never know. That's incredibly difficult and can take years."

Families are in "a black hole", crushed by their loss, but unable to start grieving and healing until the plane's fate is clear, said K.S. Narendran, a business consultant in Chennai, India, whose wife Chandrika Sharma was on board.

Resulting stress has worsened his diabetes. Neck and arm maladies also have emerged.

He copes by blogging frequently on the latest speculation, but is tormented by the lack of closure since the disaster.

"Families have reckoned with the fact that a loved one is gone," he said.

"But to put it behind us and just move on? We don't quite know how to take that next step."